A.15 Bonfire test
A.15.1 General
The
bonfire test is designed to demonstrate that
finished cylinders, complete with the
fire protection system (cylinder valve, pressure relief devices and/or integral thermal insulation) specified in the design,
will prevent the rupture
of the cylinder when tested under the specified fire conditions.
Precautions shall be
taken
during fire
testing in the event that cylinder rupture occurs.
A.15.2 Cylinder
set-up
The cylinder shall be placed horizontally with
the
cylinder bottom approximately 100 mm
above
the fire source.
Metallic shielding shall be
used to prevent
direct flame impingement on cylinder valves,
fittings, and/or pressure relief devices. The metallic shielding shall not be in
direct contact with the specified fire protection system (pressure relief devices or cylinder valve).
Any failure during the test of a valve,
fitting or tubing that is not
part
of
the intended protection
system for the design shall
invalidate the result.
A.15.3
Fire source
A uniform
fire source of 1.65 m
length shall provide direct flame
impingement
on
the
cylinder
surface across its entire diameter.
Any fuel may be
used for the fire source
provided it
supplies uniform heat sufficient to maintain the
specified test temperatures
until the cylinder is
vented.
The selection of a fuel should take into consideration air pollution concerns.
The
arrangement of the fire shall be recorded in sufficient detail to ensure that the rate of heat input to the cylinder is reproducible.
Any failure or inconsistency of the fire source during a test shall
invalidate the result.
A.15.4 Temperature
and pressure measurements
Surface temperatures shall
be monitored by at least three thermocouples located along the bottom of the
cylinder and spaced not more than 0.75
m apart.
Metallic shielding shall be
used to prevent
direct flame impingement on the thermocouples.
Alternatively, thermocouples
may
be inserted into blocks
of metal measuring less than
25
mm square.
Thermocouple temperatures
and the cylinder pressure
shall
be recorded at intervals of every 30 s
or less during the test.
A.15.5 General test requirement
The cylinder shall be
pressurized to working pressure
with natural gas or compressed air and tested in the horizontal position at working pressure
and
at 25 % of working pressure if a thermally activated PRD is not
used.
Immediately following ignition, the
fire shall produce flame impingement
on the surface
of the cylinder along
the 1,65 m length of the fire source and across the
cylinder diameter.
Within 5 min of ignition the temperature at
least one thermocouple
shall indicate a temperature
W 590 °C. This minimum temperature shall
be maintained
for the remainder
of
the test.
For cylinders
of length 1.65 m or less, the
centre of the cylinder shall be positioned over the centre of the
fire source.
For
cylinders of length greater than 1.65 m. The cylinder shall be positioned as
follows:
a)
if the cylinder is fitted with a pressure relief
device at one end, the fire source shall commence at the opposite end of
the cylinder;
b)
if the cylinder is fitted with pressure relief
devices at both ends, or at more than one
location along the length of
the
cylinder, the
centre of the fire source shall be centered midway between
the pressure
relief devices
that are separated by the greatest horizontal distance;
c)
if the cylinder is additionally protected using thermal insulation,
then two fire tests at service pressure shall be performed, one with
the fire centered midway along the cylinder length, and the other with the fire
commencing at one of the ends of a second cylinder.
A.15.6
Acceptable results
The cylinder
shall
vent through a pressure relief
device.
DESCRIPTION OF MACHINE
1. Bonfire chamber
The bonfire
chamber has been designed
for full safety. The drawing of the chamber
is as attached. The 4 walls and the roof chamber
are made of steel reinforced concrete (RC). Although there is an opening at both sides of front
wall, the front
barrier wall
is made big enough to prevent any flying out object from the blast of the CNG cylinder to
escape.
On the front wall, there is a viewing
window for the video camera.
2. Design Calculation
1. The inter size of the chamber is 3 m length x 3 m width x 2.5 m height.
This big chamber design prevent
the concrete wall damaged by blast pressure wave. The blast wave energy of a CNG cylinder of 80 liter capacity =
11.7 MJ.
2.
The walls and roof are designed
to withstand for impact of flying pieces from the cylinder blast. The
maximum velocity of projectile at blast = 33.6 m/s
(121 km/h).
The maximum impact energy on the wall = 28224 J
3.
Hence, the RC wall and roof thickness
to withstand above factors
is 20 cm and walls are standing on the strong
foundation. (The
foundation design depends on the
soil bearing capacity)
(All detail calculations will be available at the time
of contract.)
The following
figures show the design
without front barrier wall.
3. Fire source
The fire source uses the LPG fuel as shown. The length of fire source is 1.65 m.
The burner
has been designed
to have even heating along the cylinder length.
The fire source
is able to be ignited remotely.
4. Instrumentations
Three thermocouples (T) are installed on the bottom surface
of the cylinder. Two thermocouples are installed at both ends. Metallic shielding is used
to prevent direct flame impingement
on the thermocouples. The water cooled pressure transducer (P) is
installed at inlet pipe.
The machine
can
record
time, temperature, and pressure readings at 30 second intervals or less, beginning when the fire is ignited
and continuing until the pressure
release
device
releases.
SPECIFICATIONS
1.
The machine can be used to test
the CNG cylinders according to ISO11439 Annex A (normative) Test method and criteria A.15. Bonfire test.
2.
The machine can be used to test
the CNG cylinder of size: diameter
406 mm and length 1,800 mm.
3.
Bonfire chamber:
a)
Steel reinforced forced
concrete (RC) walls and
roof with sable foundation, (fire proof)
b)
Internal dimensions 3 m
Length x 3 m
Width x 2,5 m Height,
c)
thickness of walls
and
roof
20 cm
d)
The chamber geometry prevents any flying object from the
cylinder blast to escape outside chamber
e)
Test station is able to control
the temperature and pressure
in time during bonfire test
f)
The test cylinder is supported
above ground with its longitudinal axis horizontal.
4.
Fire source:
a)
Fuel LPG
b)
length 1.65 m
c)
material steel
d)
distance between the fire
source and cylinder is 100 mm
±3
e)
The fire source is able to get
the cylinder bottom
surface temperature of 590°C or more
within 5 minutes of ignition
5.
Instruments:
a)
Surface temperature is monitored by 3 thermocouples
located along the bottom of the cylinder and spaced
less than 0.75m apart. Thermocouples
are inserted into
blocks
of metal
measuring less than 25 mm square.
b)
Thermocouple type
K 0 to 1000 °C : 5 pc
c)
Pressure Transducer (water
cooled) 1000 bar 1pc for pressure measurement
of cylinder gas pressure during test.
d)
The PRD (pressure relief device) 1 pc (made of stainless steel)
e)
PC data acquisition system
(Temperature, Pressure, Time)
f)
Temperature and pressure
data are recorded at 30 second interval
or less.
6.
The bonfire test is monitored by the
software program running on Windows OS.
Data are recorded and stored in the data collection. The recorded
data can be analyzed and the graph can be plotted.
The test result is reported as number or graph and printed out on the printer.
The report format can be selected
by user.
7.
Video camera and PC
8.
Equipped with 3 set of cylinder
trolley
Please consult with our
local agent to determine your requirement.
